JP2015186380A - Power supply device and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to supply a light-emitting element with stable power.SOLUTION: The power supply device includes: a voltage conversion part that converts a power supply voltage; a constant current part that makes a current output from the voltage conversion part to be a constant current by on and off of a switching element; a voltage detector that detects a voltage output from the voltage conversion part; and a control part that, when a voltage detected by the voltage detector is lower than a preset first threshold value, makes an upper limit threshold value of the constant current small.

Description

  Embodiments described herein relate generally to a power supply device and a lighting device.

  Conventionally, for example, in a power supply device that supplies power to a load such as a light source of a lighting device, the voltage is converted by a voltage conversion circuit, and then the current is controlled by a constant current circuit to supply power to the light source. Yes.

JP 2011-109982 A

  However, in the above-described prior art, when the power supply voltage of the external power supply, for example, the AC power supply fluctuates, and there is a transient voltage fluctuation in the output voltage from the voltage conversion circuit, the output current from the constant current circuit is also transient. There was a case where it became large. For this reason, the power supply supplied to loads, such as a light source, may become unstable.

  An object of the present invention is to provide a power supply device and a lighting device that can supply a stable power source to a light emitting element.

  The power supply device of one embodiment includes a voltage conversion unit that converts a power supply voltage, a constant current unit that makes a current output from the voltage conversion unit constant by turning on and off a switching element, and an output from the voltage conversion unit. A voltage detection unit configured to detect a voltage; and a control unit configured to reduce the upper limit threshold value of the constant current when the voltage detected by the voltage detection unit is lower than a preset first threshold value.

FIG. 1 is a circuit diagram illustrating the circuit configuration of the power supply device according to the embodiment. FIG. 2 is an explanatory diagram for explaining the relationship between the converted voltage and the peak current in the constant current control.

  Hereinafter, a power supply device and an illumination device according to an embodiment will be described with reference to the drawings. In the embodiment, configurations having the same functions are denoted by the same reference numerals, and redundant description is omitted. In addition, the power supply device and illuminating device which are demonstrated by the following embodiment only show an example, and do not limit embodiment. In addition, the following embodiments may be appropriately combined within a consistent range.

  The power supply device 10 according to the embodiment described below includes a voltage conversion circuit 11 that converts a voltage, a constant current circuit 12 that uses a current output from the voltage conversion circuit 11 as a constant current, and an output from the voltage conversion circuit 11. A voltage detection circuit 108 for detecting the detected voltage, and control for narrowing the peak current value as the upper limit of the constant current to a smaller value when the detected voltage falls below a preset first threshold value (threshold value TH1). And a control circuit 120 to perform.

  In the power supply device 10 according to the embodiment described below, the control circuit 120 reduces the peak current value after the detected voltage falls below the first threshold, and then the detected voltage becomes the first threshold. In the case above, the peak current value is increased after a predetermined time delay.

  Moreover, in the power supply device 10 according to the embodiment described below, the control circuit 120 increases the peak current value when the peak current value is increased after narrowing down.

  Further, in the power supply device 10 according to the embodiment described below, the control circuit 120 allows the constant current when the detected voltage is lower than the second threshold value (threshold value TH2) set lower than the first threshold value. The circuit 12 is stopped.

  In the power supply device 10 according to the embodiment described below, the control circuit 120 restarts the constant current circuit 12 after stopping the constant current circuit 12.

  Moreover, the illuminating device 1 concerning embodiment described below comprises the power supply device 10 and the light source 21 as a load of the power supply device 10. FIG.

  FIG. 1 is a circuit diagram illustrating a circuit configuration of a power supply device 10 according to the embodiment. As illustrated in FIG. 1, the lighting device 1 includes a power supply device 10 and a light source 21 (light emitting element). The lighting device 1 may be a base light, a down light, a security light, a road light, and the like in addition to a ceiling light, and is not limited to the illustrated example.

  For example, the light source 21 may be an LED (Light Emitting Diode) element. The power supply device 10 supplies power to the light source 21 as a load, for example, turns on the light source 21. In addition, the light emitting element as the light source 21 may be a semiconductor light emitting element such as an LED, or may be an organic EL.

  As shown in FIG. 1, the power supply device 10 includes a voltage conversion circuit 11, a voltage detection circuit 108, a constant current circuit 12, and a control circuit 120, and supplies power from the constant current circuit 12 to the light source 21. Circuit configuration.

  On the input side of the voltage conversion circuit 11, an AC power supply 101, a full-wave rectifier circuit 102, and a capacitor 103 are provided. The AC power supply 101 is a commercial power supply (not shown). The AC power supply 101 is connected to the input terminal of a full-wave rectifier circuit 102. The full-wave rectification circuit 102 generates an output obtained by full-wave rectifying the AC power from the AC power supply 101. A capacitor 103 is connected between the positive and negative output terminals of the full-wave rectifier circuit 102 and constitutes a DC power source together with the full-wave rectifier circuit 102.

  The voltage conversion circuit 11 is composed of a step-up chopper circuit for converting the above-described DC power supply voltage into a predetermined voltage. Specifically, the voltage conversion circuit 11 includes a chopper choke 104, a switching element 105, a diode 106, and a smoothing capacitor 107. In the voltage conversion circuit 11, a series circuit of a chopper choke 104 and a switching element 105 such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is connected to the output terminal of the DC power supply. A series circuit of a smoothing capacitor 107 such as a diode 106 and an electrolytic capacitor is connected in parallel with the switching element 105.

  Connected between the voltage conversion circuit 11 and the constant current circuit 12 is a voltage detection circuit 108 that detects the voltage that is smoothed by the smoothing capacitor 107 and output from the voltage conversion circuit 11. The voltage detected by the voltage detection circuit 108 is output to the control circuit 120.

  The constant current circuit 12 is a circuit that uses the current output from the voltage conversion circuit 11 as a constant current. Specifically, the constant current circuit 12 includes a switching element 109, a diode 110, an inductor 111, a resistor 112, and a smoothing capacitor 113. A series circuit of a switching element 109 such as a MOSFET connected in parallel and a diode 110 is connected to the output terminal of the voltage conversion circuit 11. Further, a light source 21 is connected between the switching element 109 and the diode 110 via an inductor 111, and a smoothing capacitor 113 is connected in parallel with the light source 21. The resistor 112 is for detecting the current flowing through the light source 21. A connection point between the resistor 112 and the smoothing capacitor 113 is connected to the control circuit 120, and the control circuit 120 is based on the output from the connection point and is in proportion to the current of the light source 21 (proportional to the current of the light source 21. Current).

  The control circuit 120 is a circuit that controls on / off of the switching elements 105 and 109 of the voltage conversion circuit 11 and the constant current circuit 12. Specifically, the control circuit 120 is connected to the gates of the switching elements 105 and 109, and controls the switching operation of the switching elements 105 and 109 by PWM (Pulse Width Modulation).

  Here, the operation of the power supply apparatus 10 will be described. First, when the AC power supply 101 is turned on, a voltage rectified by the full-wave rectifier circuit 102 and smoothed by the capacitor 103 is input to the voltage conversion circuit 11.

  In the voltage conversion circuit 11, the switching element 105 is turned on / off by the control circuit 120 at a preset switching frequency. Thereby, the smoothed voltage is boosted to a predetermined voltage. Further, the boosted voltage is smoothed by the smoothing capacitor 107 and supplied to the constant current circuit 12.

  In the constant current circuit 12, the switching element 109 is turned on and off by the control circuit 120 at a preset switching frequency. Thus, the constant current circuit 12 sets the current output from the voltage conversion circuit 11 as a constant current. This constant current is supplied to the light source 21, and the light source 21 is turned on.

  During the lighting of the light source 21, the control circuit 120 supplies a predetermined maximum current to the light source 21 based on the voltage value from the voltage conversion circuit 11 detected by the voltage detection circuit 108 and the current value of the light source 21. The switching operation of the switching element 109 is feedback-controlled (constant current control) so that the constant current is less than the value (peak current). Specifically, the control circuit 120 adjusts the pulse width of the switching element 109 so that the current value of the light source 21 becomes a target value equal to or less than the peak current.

  The control circuit 120 adjusts the value of the peak current based on the voltage value from the voltage conversion circuit 11 detected by the voltage detection circuit 108. Specifically, the control circuit 120 narrows down the peak current value to a smaller value when the voltage value detected by the voltage detection circuit 108 falls below a preset threshold value (first threshold value). For example, the control circuit 120 sets 1A as the peak current value, and when the voltage value detected by the voltage detection circuit 108 falls below the first threshold, sets 0.5A as the peak current value.

  In this way, when the voltage value fluctuates low, by narrowing down the peak current value, which is the upper limit value in constant current control, even if a transient voltage fluctuation occurs such that the voltage suddenly returns thereafter, The influence on the current can be suppressed.

  FIG. 2 is an explanatory diagram for explaining the relationship between the converted voltage and the peak current in the constant current control. In FIG. 2, the upper graph shows voltage waveforms W <b> 1 and W <b> 2 after voltage conversion by the voltage conversion circuit 11. The middle and lower graphs show the peak current values in the control circuit 120 corresponding to the upper and waveform W1.

  As shown in FIG. 2, when the voltage converted by the voltage conversion circuit 11 is the waveform W1, the control circuit 120 narrows the value of the peak current to a smaller value at time t1 that is lower than the threshold value TH1. Thus, even when the voltage converted by the voltage conversion circuit 11 returns to the threshold value TH1 at the time t2 when a relatively short time T1 has elapsed, the value of the peak current is narrowed down, so that the effect on the constant current control is affected. Can be suppressed.

  Further, the control circuit 120 narrows down the peak current value because the voltage converted by the voltage conversion circuit 11 falls below the threshold value TH1, and then the voltage converted by the voltage conversion circuit 11 becomes equal to or higher than the threshold value TH1. After a predetermined time delay, the peak current value is increased to return to the value before narrowing down. Specifically, the control circuit 120 measures the time by counting the wave number of the switching frequency, and the time T2 has passed from the time t2 when the voltage after the conversion by the voltage conversion circuit 11 becomes equal to or higher than the threshold value TH1. The peak current is returned to the original value at time t4. In this way, by delaying the timing for returning the peak current value to the original value, the peak current value is narrowed down while the voltage converted by the voltage conversion circuit 11 is in the vicinity of the threshold value TH1 and changes transiently. It will remain. Therefore, the influence on the constant current control can be more reliably suppressed.

  The control circuit 120 may gradually increase (increase) the peak current value when the peak current is increased at time t4 and returned to the value before narrowing down. Specifically, the control circuit 120 returns the value of the peak current to the original value with a predetermined time width. At this time, the control circuit 120 may increase the value of the peak current step by step with a predetermined number of steps. The timing for increasing the value of the peak current may be time t2 when the voltage converted by the voltage conversion circuit 11 becomes equal to or higher than the threshold value TH1. As described above, even when the value of the peak current is increased, the influence on the constant current control can be more reliably suppressed.

  The control circuit 120 may turn off the switching element 109 and stop the constant current circuit 12 when the voltage converted by the voltage conversion circuit 11 is lower than the threshold value TH2 lower than the threshold value TH1. Specifically, when the voltage converted by the voltage conversion circuit 11 is the waveform W2, the control circuit 120 stops the constant current circuit 12 at time t3 when it falls below the threshold value TH2. In this way, when the voltage converted by the voltage conversion circuit 11 sinks greatly, the constant current circuit 12 is stopped, so that a large current is supplied to the light source 21 even if the voltage suddenly returns thereafter. Flow can be suppressed.

  The control circuit 120 may restart the constant current circuit 12 by starting the switching operation of the switching element 109 after stopping the constant current circuit 12. Specifically, the control circuit 120 restarts the constant current circuit 12 when a predetermined condition is satisfied such that the voltage converted by the voltage conversion circuit 11 recovers to the threshold value TH1. Thus, when the voltage after the conversion by the voltage conversion circuit 11 sinks greatly, the constant current circuit 12 may be stopped and then restarted to continue the constant current control.

  As described above, the power supply device 10 according to the embodiment includes the voltage conversion circuit 11 that converts the voltage, the constant current circuit 12 that uses the current output from the voltage conversion circuit 11 as a constant current, and the output from the voltage conversion circuit 11. A voltage detection circuit 108 for detecting the detected voltage, and control for narrowing the peak current value as the upper limit of the constant current to a small value when the detected voltage falls below a preset first threshold value (threshold value TH1). And a control circuit 120 for performing the above. For this reason, according to the power supply device 10 according to the embodiment, even when a transient voltage fluctuation occurs, the influence on the constant current control can be suppressed, and a stable power supply is supplied to the load (light source 21). can do.

  In the power supply device 10 according to the embodiment, the control circuit 120 reduces the peak current value after the detected voltage falls below the first threshold, and then the detected voltage becomes equal to or higher than the first threshold. In this case, the peak current value is increased after a predetermined time delay. For this reason, according to the power supply device 10 concerning embodiment, even if it is a case where a transient voltage fluctuation arises, the influence on constant current control can be suppressed more reliably.

  In the power supply device 10 according to the embodiment, when the control circuit 120 increases the peak current value after narrowing down, the peak current value is gradually increased. For this reason, according to the power supply device 10 concerning embodiment, even if it is a case where a transient voltage fluctuation arises, the influence on constant current control can be suppressed more reliably.

  In the power supply device 10 according to the embodiment, the control circuit 120 stops the constant current circuit 12 when the detected voltage falls below the second threshold value (threshold value TH2) set lower than the first threshold value. Let For this reason, according to the power supply device 10 according to the embodiment, when the voltage sinks greatly, the constant current circuit 12 is stopped, and even if the voltage suddenly returns thereafter, the light source 21 can be stopped. Can suppress the flow of a large current.

  In the power supply device 10 according to the embodiment, the control circuit 120 restarts the constant current circuit 12 after stopping the constant current circuit 12. For this reason, according to the power supply device 10 concerning embodiment, even if a voltage sinks largely, it can be restarted after stopping the constant current circuit 12, and constant current control can be continued.

  In addition, the illumination device 1 according to the embodiment includes a power supply device 10 and a light source 21 as a load of the power supply device 10. For this reason, in the illuminating device 1 concerning embodiment, the stable power supply can be supplied with respect to the light source 21. FIG.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Illuminating device, 10 ... Power supply device, 11 ... Voltage conversion circuit, 12 ... Constant current circuit, 21 ... Light source (light emitting element), 101 ... AC power supply, 102 ... Full wave rectifier circuit, 103 ... Capacitor, 104 ... Chopper choke , 105 ... switching element, 106 ... diode, 107 ... smoothing capacitor, 108 ... voltage detection circuit, 109 ... switching element, 110 ... diode, 111 ... inductor, 112 ... resistance, 113 ... smoothing capacitor, 120 ... control circuit, t1- t4 ... time, T1, T2 ... time, TH1, TH2 ... threshold, W1, W2 ... waveform

Claims (6)

A voltage converter for converting the power supply voltage;
A constant current unit that sets the current output from the voltage conversion unit to a constant current by turning on and off the switching element;
A voltage detector for detecting a voltage output from the voltage converter;
A control unit that reduces the upper limit threshold of the constant current when the voltage detected by the voltage detection unit is lower than a preset first threshold;
A power supply apparatus comprising: The controller detects the voltage detected by the voltage detector above the first threshold after the voltage detected by the voltage detector is less than the first threshold and reduces the upper limit threshold of the constant current. 2. The power supply device according to claim 1, wherein, when it becomes, the upper limit threshold of the constant current is increased after a predetermined time delay. 3. The control unit according to claim 1, wherein when the upper limit threshold of the constant current is increased again after reducing the upper limit threshold of the constant current, the control unit increases the upper limit threshold of the constant current. Power supply. The control unit stops the constant current unit when a voltage detected by the voltage detection unit falls below a second threshold set lower than the first threshold. The power supply apparatus as described in any one of thru | or 3. The power supply device according to claim 4, wherein the control unit restarts the constant current unit after stopping the constant current unit. A power supply device according to any one of claims 1 to 5;
A light emitting element;
A lighting device comprising:

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